If you would like one side to go off realism, then the other side should to for consistency. You ever see an entire city of people ignore all traffic lights/laws, all drive sports cars/bikes and consistently drive 200+ everywhere they go? More than likely the answer is no. Law enforcement is not a proactive faction, they are reactive. If every criminal they come up against is evading on a high speed motorcycle or sports car, PD works with the government to obtain one to deal with them, as they cannot just let the criminals do whatever they please.
As for your comment regarding the number of units at a traffic stop or pursuit, that is all dictated by IC protocols within PD. If PD pulls someone over that tends to evade 90% of the time, then we make sure to get multiple backup units and the appropriate response vehicles to deal with it. As I said, its reactionary response. If someone that PD has never seen before gets pulled over and they have a fairly clean record, then no backup is asked for.
I agree it should be fair for both sides as well. But do you think its fun for PD to see criminals drive by going 200+ in the city on drags/shinobis non-stop and have 0 chance to do anything about it? Deployment of the high speed resources is strictly limited for a reason. PD cannot just patrol around in a high speed car or bike for no reason.
Lastly, to your original point about realism...do you think it would be realistic for criminals to be stronger than law enforcement? Have the whole city run by gangs and PD would be powerless to stop them because they have less firepower, less resources, less equipment? Its not realistic in any sense to have criminals overtake the city and to just have it fall and burn because law enforcement cannot do anything about it.